1α, 25-Dihydroxyvitamin D₃ and the vitamin D receptor regulates ΔNp63α levels and keratinocyte proliferation

Cell Death Dis. 2015 Jun 11;6(6):e1781. doi: 10.1038/cddis.2015.148.

Abstract

1α, 25-dihydroxyvitamin D3 (VD3), a secosteriod that has been explored as an anti-cancer agent, was also shown to promote cell survival. Its receptor, the Vitamin D Receptor (VDR), is a direct target of the proto-oncogene ΔNp63α, which is overexpressed in non-melanoma skin cancers. The interconnection between VDR/VD3 signaling and ΔNp63α, led us to examine whether VDR/VD3 signaling promotes keratinocyte proliferation by regulating ΔNp63α levels. Our data demonstrate that VDR regulates ΔNp63α expression at both the transcript and protein level. Interestingly, although low doses of VD3 led to an increase in ΔNp63α protein levels and keratinocyte proliferation, high doses of VD3 failed to increase ΔNp63α protein levels and resulted in reduced proliferation. Increased expression of ΔNp63α by low dose VD3 was shown to be dependent on VDR and critical for the proliferative effects of VD3. VD3-mediated increases in ΔNp63α protein levels occur via activation of both p38 MAPK and Akt kinases. Finally, analysis of samples from patients with squamous cell carcinoma (SCC), basal cell carcinoma and precursors to invasive SCC demonstrated a significant correlation between p63 and VDR levels when compared with healthy normal skin control samples. Delineation of the mechanisms by which VD3 exerts its effect on ΔNp63α and cell proliferation is critical for determining the future of VD3 in cancer therapies.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Carcinoma, Basal Cell / pathology
  • Carcinoma, Squamous Cell / pathology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Cell Survival / drug effects
  • Cholecalciferol / pharmacology*
  • Heterocyclic Compounds, 3-Ring / pharmacology
  • Humans
  • Imidazoles / pharmacology
  • Keratinocytes / metabolism*
  • Naphthalenes / pharmacology
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Pyrazoles / pharmacology
  • Pyridines / pharmacology
  • RNA Interference
  • RNA, Small Interfering
  • Receptors, Calcitriol / genetics
  • Receptors, Calcitriol / metabolism*
  • Signal Transduction
  • Skin Neoplasms / pathology
  • Transcription Factors / biosynthesis
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Tumor Suppressor Proteins / biosynthesis
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*
  • p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors

Substances

  • BIRB 796
  • Heterocyclic Compounds, 3-Ring
  • Imidazoles
  • MK 2206
  • Naphthalenes
  • Pyrazoles
  • Pyridines
  • RNA, Small Interfering
  • Receptors, Calcitriol
  • TP63 protein, human
  • Transcription Factors
  • Tumor Suppressor Proteins
  • VDR protein, human
  • Cholecalciferol
  • Proto-Oncogene Proteins c-akt
  • p38 Mitogen-Activated Protein Kinases
  • 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole